The paper sheet processing apparatus disclosed in Patent Document 1 is equipped, as processing means, with a cutting device section having a slitter processing unit; an optional processing device section in which one of plural kinds of processing units (such as a perforation forming unit and a crease forming unit) can be mounted; a lateral cutting device section having a cutter processing unit; and a lateral crease forming device section having a crease forming unit, and a processing unit to be mounted in the optional processing device section is selected according to the processing condition for paper sheets. Furthermore, the paper sheet processing apparatus disclosed in Patent Document 2 has a plurality of accommodating spaces in which processing modules can be mounted, and a processing module selected from among plural kinds of processing modules is mounted according to the processing condition for paper sheets.